The present invention relates generally to coated cables, and more particularly, to thermoplastic coated cables for use in applications in which enhanced visibility of same is advantageous, such as in support cables, animal tie-outs and restraints, fences, barriers and walkways.
The prior art does not adequately address the need for a coated cable which, by virtue of visual properties, could provide improved viewability, particularly at night or when used in a darkened indoor application.
It is an object of the invention to provide a coated cable which overcomes the drawbacks of the prior art.
It is a further object of the invention to provide a coated cable which provides enhanced viewability at night or in darkened surroundings.
It is a still further object of the invention to provide a coated cable with glow-in-the-dark properties such that it emits visible light in a darkened setting over an extended period of time after exposure to ambient light or other naturally or artificially applied light source.
It is a yet a further object of the invention to provide a cable with such properties in a manner which is cost effective such that a product fashioned from such cable material will be economically feasible.
Briefly stated, there is provided a cable comprised of a structural core made of twined wire or other suitable material, including for example natural or man-made non-metallic rope or filament such as cotton, hemp, nylon, etc., advantageously providing desirable flexibility and sufficient tensile strength for the particular application to which the completed cable is directed. The cable further includes an outer layer surrounding the structural core, such outer layer having glow-in-the-dark properties. The outer layer is of a material comprised of an advantageously homogeneous mixture of a suitably resilient thermoplastic and a granulated or powderized material which emits light in a darkened environment after exposure to light. A coloring agent compatible with the glow-in-the-dark component, i.e. free of components which might otherwise decay the light emissive properties thereof, may optionally be added to increase visual vibrancy in lighted situations and also to enhance the aesthetic appeal in light and dark situations as desired.
In a particularly advantageous embodiment, there is provided a cable of coaxially laminated structure, which includes a structural core as described above, an inner layer surrounding the structural core, and an outer layer, or xe2x80x9cskinxe2x80x9d, surrounding the inner layer. The inner core presents a light colored or reflective outer surface such that a major portion of incident light striking the surface is reflected back. This is accomplished conveniently by comprising the inner core of a white pigmented thermoplastic composition, advantageously opaque to mask the central structural core. Such white pigment may include for example titanium dioxide. Optionally, an optical brightener may be added to the thermoplastic composition of the inner layer to increase incident light reflectivity. Alternatively, a lightly colored or reflective coating may be applied to the inner layer, the actual color of which is therefore inconsequential. This may be in the form of paint, die, applied tape or the like. The outer layer or xe2x80x9cskinxe2x80x9d disposed coaxially about the inner layer which includes the light reflective coating, if such is used, is comprised of a thermoplastic composition which includes a material advantageously dispersed homogeneously therethrough, and which imparts glow-in-the-dark properties thereto. As noted above herein, a coloring agent compatible with the glow-in-the-dark component may optionally be added to the composition comprising the outer layer so as not to decay the light emissive properties thereof. The outer layer may be relatively thin compared with a cross-sectional diameter of the overall cable structure, and in fact is advantageously thin enough to provide translucency, thereby permitting light transmission from an outer surface thereof to the inner light enhancing layer. By reducing the amount of material used for the outer glow-in-the-dark layer, such embodiment has the advantage of economy, given the relatively high cost of the light emissive additive.
The various embodiments as disclosed herein may be conveniently produced by a cable extrusion process in which a structural core, for example a length of galvanized steel aircraft wire, is drawn through one or more suitably configured cross-heads fed by one or more extruders, the later which heat a thermoplastic to a flowable state, and the former which coat the cable core passing therethrough.